An invasion of non-venomous fried egg jellyfish this summer was likely caused by high sea temperatures and more nutrients in the sea, according to a marine biologist.
“We had the largest bloom of fried egg jellyfish this year, at least since we began the spot the jellyfish campaign in 2010,” Alan Deidun said.
Fried-egg jellyfish are distinguished by their dome-like shape and yellowish colour, which is peppered with small purple dots.
Despite their large size, such jellyfish are generally harmless to humans with little to no sting.
He said that Malta’s prolonged heatwave in summer was one possible reason for the fried egg bloom, which love high sea temperatures.
Malta sizzled last July, with temperatures soaring above 40°C for an entire week.
Sea temperatures also rose significantly above the norm, exceeding 30°C in August, Deidun said. Usually, such sea temperatures are recorded towards the end of September.
Higher sea temperatures mean a faster rate of spawning and development, Deidun said.
“The jellyfish reach larger sizes faster and this results in a higher rate of survival as they would not be eaten that easily by predators,” he said.
Another reason for the impressive number of jellyfish this year could be down to the presence of more nutrients in the sea, Deidun said.
This is probably coming from increased aquaculture activity in fish farms and from treated sewage, he said.
Treated sewage does not contain harmful bacteria but it is still full of nitrates and phosphates that plankton feed on, he added.
As plankton grows in number because of the added food supply, jellyfish have more to eat.
“It’s like throwing fertilisers in the sea,” he said.
Still, the species could be a threat to the marine ecosystem.
“They feed on plankton just like many species of fish, meaning there is increased competition,” Deidun said.
Several took the chance to swim alongside the colourful creatures, including Owen Caruana, who was on Malta’s west coast when he spotted a large school of the species towards Fomm Ir-Riħ.
“I knew they were harmless but they’re intimidating up close,” the 30-year-old said.
“Some were as big as a beach ball. Still, I jumped in and snorkelled alongside them and even touched a few,” he said.